The vertical structure of snow clouds was observed at Otaru, Hokkaido in the winter of 1970, utilizing snow crystal sondes. The following results were obtained.
1. The vertical distribution of snow crystal shape agreed well with that expected from Nakaya's Ta-s diagram. This agreement shows that the snow crystals fell, as they were, without any effect of strong updraft at side of the clouds.
2. Snow clouds of various grades of glaciation were observed: namely the early stage where the concentration of snow crystals is very small, the mature stage where the solid water content is comparable with the liquid water content, and the decaying stage where no cloud droplets were observed.
3. The growth rate of falling snow crystals was measured by the use of vertical distribution of diameter of the largest snow crystals at each level. The growth rate of snow crystals near the cloud top (in the initial stage of snow crystals) roughly coincided with those experimentally measured or theoretically calculated, however the growth rate in the middle or the lower layer of clouds (in the later stage of snow crystals) was much smaller than that near the cloud top. The small growth rate in the lower layer was considered to be because of the lack of cloud droplets in the layer.
4. The concentration of snow crystals was two or three orders greater than that of ice nuclei, even when the summit temperature of the clouds was considered. It was considered that the rapid freezing phenomena other than the riming phenomenon was related to the multiplication of ice nuclei.
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